The present invention relates generally to methods of forming metal structures in semiconductor devices and specifically to methods of depositing tungsten metal structures on silicon semiconductor structures.
Deposition of tungsten (W) involves the use of a WF6 compound as the source of tungsten. Fluorine (F) attack of the silicon (Si) substrate presents a continuing problem.
U.S. Pat. No. 6,099,904 to Mak et al. describes a tungsten process with a nucleation step.
U.S. Pat. No. 6,096,651 to Wang et al., U.S. Pat. No. 6,066,366 to Berenbaum et al., U.S. Pat. No. Re 36,663 to Smith et al., and U.S. Pat. No. 5,981,352 to Zhao et al. each describe various tungsten deposition processes.
Accordingly, it is an object of the present invention to provide a method to fabricate metal structures that minimizes fluorine attack.
Another object of the present invention is to provide a method to fabricate tungsten metal structures over silicon semiconductor structures that minimizes fluorine attack.
Other Objects will appear Hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a silicon substrate is having a patterned dielectric layer formed thereon defining a tungsten structure opening is provided. The silicon substrate is pre-heated to a temperature of from about 430 to 440xc2x0 C. A Si-rich WSix layer is formed over the patterned dielectric layer, lining the tungsten structure opening. A WSix nucleation layer is formed over the Si-rich WSix layer. A tungsten bulk layer is formed over the WSix nucleation layer, filling the tungsten structure opening, whereby fluorine attack of the Si substrate is minimized.